The Second Cthulhu Companion. Contains articles on various aspects of the game, including two 1920s scenarios: 'The Underground Menace' and 'Valley of the Four Shrines'.

From the back cover:
"Call of Cthulhu Questions Answered - Why does it take so long to read a Mythos tome? Why can't my investigator get 'used to' seeing common types of monsters? How do I learn a language in Call of Cthulhu? Must my character lose multiple Sanity for seeing multiple monsters?

The Ubiquity of Cthulhu - Working from the notes of brave Dr. Phileus P. Sadowsky (deceased), William Hamblin assembles ancient linguistic traces of the dread Cthulhu cult.

A Cthulhu Grimoire - Working summaries of all the spells from supplements Shadows of Yog-Sothoth, The Asylum, Cthulhu Companion, The Fungi from Yuggoth, Curse of the Chthonians, Trail of Tsathogghua, Masks of Nyarlathotep, and Fragments of Fear. Indispensible to keepers; deservedly horrifying to peeping players.

Scenario - The Underground Menace - Earthquakes hammer a hamlet in northern Michigan, but the townsfolk refuse to talk about the matter.